Machine tool for cutting an assembly of coaxial tubes into parts, particularly the channels of a pressure-tube nuclear reactor



ay 8, 1968 1.. DI PIAZZA ETAL 3,385,143

MACHINE TOOL FOR CUTTING AN ASSEMBLY OF COAXIAL TUBES INTO PARTSPARTICULARLY THE CHANNELS OF A PRESSURE-TUBE NUCLEAR REACTOR Filed April15, 1965 4 2 Sheets-Sheet 1 5 A 1- 12 K i "x l L r H 1 J phlmn'ij r K XINVEN-TORS Learco DI PIAZZA Rene LEROY y Ermelino MONZANI FIG. 4b

M y 28, 1968 L. Di PIAZZA ETAL 3,385,148

MACHINE TOOL FOR CUTTING AN ASSEMBLY OF COAXIAL TUBES IN-TO PARTS,PARTICULARLY THE CHANNELS OF A PRESSURE-TUBE NUCLEAR REACTOR Filed April15, 1966 2 SheetsSheet 2 FIG. 5

INVENTORS Lecrco DI PIAZZA Rene LEROY Ermelino MONZANI FIG. 3 "a 17ATTORNEYS United States Patent 3,385,148 MACHINE TOOL FOR CUTTING ANASSEMBLY OF COAXIAL TUBES INTO PARTS, PARTICU- LARLY THE CHANNELS OF APRESSURE-TUBE NUCLEAR REACTOR Learco Di Piazza, Bodio, Ren Leroy,Comerico, and

Ermelino Monzani, Milan, Italy, assignors to European Atomic EnergyCommunity-Euratonr, Brussels, Belgium Filed Apr. 13, 1965, Ser. No.447,717 Claims priority, application Belgium, Apr. 16, 1964, 519,192Claims. (Cl. 82-702) The present invention relates to a cutting-wheelmachine tool for cutting into parts the assembly of coaxial tubes and iti particularly adapted, although not exclusively so for cuttingoperations in a nuclear installation such as a pressure-tube nuclearreactor.

As is known, in certainn types of reactors moderated with heavy waterand cooled by an organic liquid, an arrangement of the refrigerantchannels has been proposed which is characterized by an assembly ofseveral concentric tubes, the outer one of which intended to resist thepressure of the refrigerant being called the pressure-tube. At variouslevels along such a channel, there is a single tube or two or threecoaxial tubes, not counting the fuel element which is mounted insidethese tubes. Also, the materials of the tubes being different, differentmaterials are met from one level to the other.

In fact, in the specific case of the reactor in question, the followingmaterials are met at different levels:

Stainless steel type 18/8 Allied steel, type Z30-C13 Sintered aluminiumcontaining high percentages of alumina and known under the sigla S.A.P.(sintered aluminium powder) Zirconium alloy of the type called Zircalloy2 Aluminium type ASNET Aluminium alloy, type AG3NET, known under thename Duralinox.

Furthermore, the tubes which have a thickness in the order of 2 mm. arearranged one within the other with a free spacing, that is, bracing ofthe tubes is provided only at the ends thereof or they are solid withthe tank of the moderator.

Besides, if the refrigerant that passes through the free spaces betweenthe tubes is a mixture of terphenyls, there is a danger that in the caseof a fault in the circulation of the refrigerant fluid, frozen terphenylmay be found between two concentric tubes.

The necessity to section the cooling channel, formed of such a pluralityof tubes and of such materials, in order to be able to remove therefroma fuel element that has become jammed following an accident, haspresented to i the technicians the problem of the choice of a cuttingmachine capable of overcoming the following difiiculties:

having a multi-purpose cutting tool capable of cutting differentmaterials,

adapting thereto the cutting fluid and limiting the sure contaminationthereof,

overcoming the wear of the tool and the resharpening problems,

perfectly circumscribing the zone where the chips fall,

solidly joining the concentric tubes together, and

ice

avoiding burning of the chips of inflammable materials,

such a the Zircalloy.

According to the invention, machine-tool for cutting an assembly ofconcentric tubes and capable of eliminating the aforementioned drawbacksis characterized by the fact that it comprises at least three cuttingwheels or discs the upper plane of which has a slight incline up to thebevelled edge of the wheel, the bevel having a still more pronouncedincline in relation to the horizontal plane, preferably of an angle of10, the cutting discs being distributed equidistantly on a circle aroundthe floating tubes and driven into a radial forward displacement.

The cutting-disc tool is indeed suitable for different materials, itdoes not produce any chips, it does not require cutting fluid, it doesnot produce overheating and it does not require sharpening.

By a circular equidistant arrangement of several cuttingdiscs of aparticular type which makes them self-centering, the rigidity of theconcentric tubes is no longer important.

The sectioning machine of the invention is further characterized in thatthe cutting-disc supports are mounted circularly equidistantly on afirst annular rotary plate through which the tubes to be sectionedextend, the disc supports being kinematically connected to elementsresponsible for the radial displacement of the discs.

More specifically, the disc supports are guided into grooves in thefirst rotary plate and kinematically engaged in a fiat Archimedean screwwhich is part of a second rotary plate similar to and facing the firstplate. A set of pinions coupled to the said plates ensures a differentnumber of turns for the two plates and causes radial displacement of thedisc supports. The cutting-discs are mounted on the machine in theradial plane of the tubes to be sectioned.

In this manner, self-centering of the tubes is obtained as well as acontinuous application of the cutting-discs.

A non-limitative embodiment of a sectioning-machine will now bedescribed with reference to the appended drawings wherein:

FIG. 1 is a diagrammatic side elevation view of the simplifiedmechanical arrangement of the machine;

FIG. 2 is a diagrammatic plan view of the essential members of themachine;

FIG. 3 is a kinematic diagram of the machine;

FIGS. 4a and 4b are transverse cross-sectional views of a cutting-disc;and

FIG. 5 is a vertical cross-sectional view of one half of the machine,the latter being in oblique position on an assembly of coaxial tubes.

Referring first to FIGS. 1 and 2, there is shown the body 1 of thesectioning-machine, the lower table 2 supporting the tools and mountedon four legs 3, the upper table 4 fixed to the lower table 2 by means ofbraces and a yoke 6 for guiding the assembly of tubes to be sectioned.

According to the invention, five cutting-tool units are mounted on afirst annular rotary plate 9 through which the coaxial tubes 10, 10" and10 (see FIG. 2) to be sectioned extend. Each unit is constituted by acutting-disc support or disc-carrier 7 and the self-centeringcutting-disc 8 proper having a cutting edge.

The disc-carriers 7 are kinematically coupled to members intended tocause the necessary forward and rearward radial displacement of thediscs.

These members, as shown in FIG. 3, comprise a second rotary plate 11similar to and disposed in front of 3 the first plate 9 and the set ofpinions 1216 with the driving motor 17.

It is pointed out that pinion 13 is interchangeable with pinions havinga different number of teeth and that pinion 14 is only an auxiliarywhee-l for reversing the direction of rotation so that plates 9 and 11rotate in the same direction.

Pinion 14 is adjustably mounted on the frame of the machine to be ableto adapt the set of pinions to the specific pinion that has been chosenas pinion 13.

The disc-carriers 7 are in double engagement in this kinematic drive,that is, by their lower part they are guided in radial grooves of thefirst plate 9 whereas by their upper part (see FIG. 2) they mesh with anArchimedean fiat screw on the lower face of the second plate 11. Whenthe pinion assembly 12 to 16 displaces plates 9 and 11 (the latter carryteeth at the periphery) the discs carriers, because of the differentrotary speeds, of the plates, are displaced radially (either toward theaxes of symmetry 18 of the machine or away therefrom).

As will be gathered from FIG. 4, the discs have a particular geometricalshape, designed from practical experiments, which makes it possible toobtain self-centering of the tubes and a constant application of thediscs themselves on the tubes.

Indeed, if fiat cutting-discs were used, the tubes which are neverneither accurately centered nor accurately cylindrical would only bepartially cut and the disc entering into the cut part would not offerany reaction to the discs still in action, the tube would then tend tobe displaced in the cutting plane which would prevent the completesectioning thereof. In order to overcome this drawback, thecutting-discs are provided with an inclined face which makes it possibleto continuously provide a reaction even when the tube is partially cut.This incline must not however be too steep in order to avoid thecreation of a vertical reaction which would tend to lift thetube andundesirably increase the power necessary for the sectioning operation.Experimentally, an angle of 2 up to the bevelled edge and an angle of 10for the bevelled edge itself have been adopted; these angles areindicated by and ,8 on FIG. 4. Angle 7 has a value of 30.

The dimensions of the cutting-discs used were as follows: diameter 90mm.; thickness 5.5 mm.; width of the upper bevelled edge 10 mm.; widthof the lower bevelled edge mm.; radius of the tip of the edge 0.2 mm.The cutting-discs were made of tool steel, chromium, of high hardness,wear resistant, trademark Cogne type SOR Z/HCS.

Referring now to FIG. 5, the specific elements of the machine as well asits operation will now be described. FIG. 5 illustrates the portion ofFIG. 1 which is circumsoribed by the line V.

In FIG. 5 is again seen the set of pinions 12 to 16, the rotary plates 9and 1 1, a disc-carrier 7 (self-centering jaws), tables 2 and 4 of theframe of the machine, braces 5 in the form of bolts and tubes 10" to besectioned.

The set of pinions is mainly constituted by two propelling systems,namely a shaft 19 with driving pulley, with pinion 12 at the bottom andwith pinion 13 at the top and a transmission shaft 21 with pinion 15 atthe top and pinion 16 at the bottom. Auxiliary pinion 14 of FIG. 3 isnot visible.

The rotary plates 9 and 11 provided with teeth 9a and 11a are housed andfreely retained between corresponding radial shoulders of cylindricalsleeves 22 and 23 and sleeves 24 and 25 in the annular space of theplates. Sleeves 24 and 25, which serve as a support for sleeves 22 and23, are secured to the tables 4 and 2 of the frame, respectively, thatis the upper sleeve is made solid with table 4 at the top by means of anut 26. For this purpose, sleeve 24 has a corresponding threading 27.Table 4 is held in place by the aforementioned bolts 5. By acting 4 onscrew 26, it is possible to adjust the seat of the rotary disc 11between sleeves 22 and 24.

The lower rotary plate 9 is also secured in position by a nut 28,screwed on thread 29 of the corresponding sleeve 25. This sleeve is madesolid with the lower disc 2 or" the body through screws 30.

The lower plate 9 carries on its upper surface shoulders 31 havingopposed radially directed guiding grooves for the reception of thecutting-disc carriers 7 through the lower part thereof; the upper plate11 has an Archimedean screw 32 on the lower surface thereof for theguiding of the cutting-disc carrier through the upper portion thereof.

The disc-carriers 7 then have at the top thereof teeth 33 in the formand of the pitch of the Archimedean screw; in their lower part, they areformed with a dovetail projection 34.

In order to secure the cutting-discs 8, an opening 35 is machined in thebody of each disc-carrier. The axes 8a of the disc is secured invertical position between the jaws of this opening in such a manner thatthey are freely rotatable.

Rotation of the lower plate 9 alone creates the orbital displacement ofthe discs around the tubes to be sectioned and rotation of the discsproper. The simultaneous but differed rotation of the upper plate 11, inthe same direction, ensures the radial displacement of the discs.

Operation of the machine of the invention is as follows:

The assembly of the tubes to be sectioned is introduced vertically andloosely in the bore 36 of the machine until the desired level isreached. Securcment of the upper part is achieved for example by theguiding yoke 6, if this cannot be obtained by means of its very weight.Motor 17 is then driven into rotation to produce displacement of thediscs towards the tubes to be sectioned. In practice, a forward movementof 0.028 mm. per turn has been adopted by using an appropriate pinion 13in the pinion train above mentioned. Sectioning then takes place withoutdifiiculty and rapidly.

The cuts thus obtained, even for a thickness of tubes of 0.6 mm. only,are clean, without deformation of the tubes and more important withoutthe creation of chips.

At the end of the sectioning operation, the cuttingdiscs are freed fromthe tubes by rapid displacement of the discs-carriers. For this purpose,the lower plate is locked and the upper plate alone is driven in adirection reverse that of the initial rotation.

By way of example, a kinematic drive for a machine with central bore of15 cm. is characterized by the following ratios (in number of teeth):pinion 12: 86 teeth; pinion 13: teeth; pinion 14: 40 teeth; pinion 15:64 teeth; pinion 16: 65 teeth; teething of plates 9 and 11: .190 teeth.The pitch of the Archimedean is 7.25 mm. The speed of the upper plate:50 r.p.m. The power of the 220 volts A.C. electric driving motor: 3.5HP.

We claim:

1. A cutting machine for sectioning tubes coaxially and loosely mountedone into the other, comprising:

(a) at least three generally horizontal cutting discs each having anupper face and a cutting bevelled edge; said upper face decliningslightly from the center thereof toward said bevelled edge in relationto the horizontal plane and said edge declining more sharply than saidupper face in relation to said plane;

(b) means mounting said cutting discs equidistantly around said tubes,and

(c) means causing radial displacement of said discs in relation to saidtubes.

2. A cutting machine as claimed in claim 1, wherein the bevelled edgeincline is of the order of 10.

3. A cutting machine as claimed in claim 1, wherein said mounting meansincludes a first rotary annular plate mounted around said tubes anddisc-carriers evenly distributed on said first plate and in kinematicengagement with said displacement means.

4. A cutting machine as claimed in claim 2, wherein said disc-carriersare guided into radially directed grooves on said first plate and saiddisplacement means comprises:

a second annular rotary plate mounted above the first plate;

Archimedean screw means on said second plate and said disc-carrierscapable of causing axial displacement of the carriers, and

means to cause relative rotation of said first and secand plates toproduce radial displacement of said carriers and discs relative to saidtubes to be seetioned.

5. A cutting machine as claimed in claim 4, including a pair of spacedupper and lower tables having a bore through the center thereof for thepassage of the tubes to be sectioned; means to secure said tubes to saidtables, and means to mount said plates between said tables.

No references cited.

HARRISON L. HINSON, Primary Examiner.

1. A CUTTING MACHINE FOR SECTIONING TUBES COAXIALLY AND LOOSELY MOUNTEDONE INTO THE OTHER, COMPRISING: (A) AT LEAST THREE GENERALLY HORIZONTALCUTTING DISCS EACH HAVING AN UPPER FACE AND A CUTTING BEVELLED EDGE;SAID UPPER FACE DECLINING SLIGHTLY FROM THE CENTER THEREOF TOWARD SAIDBEVELLED EDGE IN RELATION TO THE HORIZONTAL PLANE AND SAID EDGEDECLINING MORE SHARPLY THAN SAID UPPER FACE IN RELATION TO SAID PLANE;(B) MEANS MOUNTING SAID CUTTING DISCS EQUIDISTANTLY AROUND SAID TUBES,AND (C) MEANS CAUSING RADIAL DISPLACEMENT OF SAID DISCS IN RELATION TOSAID TUBES.